18036373140domain: NAppears in sequences"CHK" (necklace, identity, unlabeled) transform of 1, 2, 3, 4, ...at n=27A032170Inverse EULER transform of A064831 (with its initial 1 omitted).at n=28A072337a(n) = (1/n) * Sum_{d|n} moebius(n/d) * Lucas(d)^2, where Lucas(n) = A000204(n).at n=27A203853